Controlled belt drive



1955 E. J. JUSTUS ETAL 3,209,607

CONTROLLED BELT DRIVE Filed Nov. 28, 1962 5 Sheets-Sheet l v I N ll l PRIME MOVER INVENTORS Edgar J 70$ #05 BY Leroy H. Husker 1965 E. .1. JUSTUS ETAL 3,209,607

CONTROLLED BELT DRIVE Filed Nov. 28, 1962 5 Sheets-Sheet 2 u i E 35 k "o "4 a: a a I w E a o Iw k g in H9 s] Q (a) aFE'dJ "/0 '0 E f g l n n i INVENTORS fo'gor .7. Juszus BY Leroy H. Bus/eel M and o4 ATORNEYS Oct. 5, 1965 E. J. JUSTUS ETAL 3,209,607

CONTROLLED BELT DRIVE Filed NOV. 28, 1962 5 Sheets-Sheet 3 INVENTORS Edgar .7. Juszus BY Leroy h, Busker' Oct. 5, 1965 E. J. JUSTUS ETAL 3,209,507

CONTROLLED BELT DRIVE Filed Nov. 28, 1962 5 Sheets-Sheet 5 27 E INVENTORS Edgar .7. Jusfus Ler'oy H. Buser M w, a, v A TORNEYS United States Patent 3,209,607 CONTROLLED BELT DR'IVE Edgar J. Justus, Beloit, Wis, and Leroy H. Busker, Rockton, 11]., assignors to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Nov- 28, 1962, Ser. No. 240,546 1'3 Claims. (CL 74--216.5)

The present invention relates to improvements in papermaking machines and more particularly to an improved belt drive and control whereby a very uniform output speed can be obtained and the output speed does not vary with changes in load.

The operating speed of different sections of a paper machine is adjustable and once a machine is running smoothly it is of critical importance to maintain a uniform relative speed between the sections. The speed between the sections determines the draw or the tension of the paper web as it passes from one section to another, and if the draw tightens the sheet too much the paper web will break requiring an expensive shutdown of the machine or if the draw slackens other troubles occur such as wrinkling.

A common type of drive used for a Fourdrinier section of a paper machine is a cone pulley drive wherein the cones are arranged to have reversed tapers so that the sums of the diameters of the two pulleys are equal for all positions of the drive belt which runs over the pulleys. The belt is changed by a belt shifter for obtaining a desired drive speed. Once the proper speed of drive for the Fourdrinier section is obtained, changes in operating conditions will change the amount of driving power required which will in turn cause changes in speed of the Fonrdrinier wire due to increase or decrease in changes of creep of the driving belt. For example, a change in freeness or consistency of the paper-making stock will result in a change in suction box vacuum requirements due to changes in drainage characteristics, and consequently the Fourdrinier drag on the suction box will change to alter the required driving power. It is critical that with any such change readjustment of the Fourdrinier speed must be made rapidly to maintain a uniform speed so that the paper web will maintain a constant relationship at the open draw relative to the next section of the paper machine.

Similar problems occur in other machinery such as coaters, laminaters and waxers in which moisture addition to the sheet changes its length, tension, and hence the drive requirements. Other machines have requirements for maintaining constant speed with changes in load and the problem of change in belt creep is always present in a cone pulley belt drive where changes of load occur.

It is accordingly an important objective of the present invention to provide an improved cone pulley belt drive capable of maintaining a more uniform output speed with changes in load than obtainable with the devices heretofore available.

One arrangement previously employed for maintaining constant speed in this type of device utilizes a speed measuring device wherein the speed of the output pulley or shaft is measured and a correction signal is fed back into the machine by shifting the position of the belt on the cone pulleys as soon as the output speed changes due to change in load. Such systems are limited in their operational capabilities because of the problem of hunting. Another disadvantage of such control arrangements is the high cost of the speed measuring devices.

An important feature of the present invention is related to the discovery that under dynamic conditions the percentage creep of a driving belt is a linear function of the transmitted torque by the belt and is therefore relatively easily reproduced for any particular type of belt by merely determining creep under no load and full load conditions.

It has been assumed heretofore that creep is a linear function of belt tension and may be expressed by the following relation:

Percent creep= AX E in which:

T =tight side belt tension in pounds T =slack side belt tension in pounds A =cross sectional area of belt in square inches E =rnodulus of elasticity of belt material in p.s.i.

It has been discovered that creep is not a function of strain due to load torque alone but is actually a complex function of many factors which may be expressed in a general way as follows:

Percent creep-:function of (load torque strain bending strain friction force strain interface shear strain).

The last term of this expression takes into account the shear deformation as a result of bending forces and friction forces of the interface material if the belt consists of a nylon core with a leather interface between core and pulley.

The expression for creep in terms of the variables now becomes:

L 1 1 i 1 Percent creep- Tb Es+Esi in which:

T =effective tension in pounds A=cross sectional area of belt in sq. inches E :modulus of elasticity of belt, p.s.i.

t=belt thickness, inches r=pulley radius in feet a coefficient of friction between belt and pulley T =tight side belt tension, pounds b=belt width inches E =Shear modulus of belt material, p.s.i. t =thickness of interface, inches E =shear modulus of interface material, p.s,i.

Additional factors will enter in that in most cases will be empirical. The creep calculation can be simplified by using an expression involving only the simple strain and to account for the other factors by using a dynamic modulus.

The expression for creep may then be set forth:

100 T T Percent creep X Ed in which:

E is the dynamic modulus of the belt material.

J) measured and compared with its associated creep value. After comparison is made the driving belt is shifted on the cone pulleys so as to compensate for speed variations.

An object of the present invention is to provide an improved control for a variable speed cone pulley drive which obtains uniform output speed without over compensation or hunting.

Another object of the invention is to provide an improved drive for a section of a papermaking machine and particularly for a Fourdrinier machine embodying cone pulleys wherein Changes in machine load do not cause changes in drive speed to change in belt creep.

A still further object of the invention is to provide an improved cone belt drive wherein changes in belt creep which tend to cause output speed changes are immediately compensated for by measuring the torque of the drive and shifting the belt position as a function of torque change an amount to compensate for change in creep.

Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiment thereof in the specification, claims and drawings, in which:

FIGURE 1 is a top plan view shown schematically of a Fourdrinier section of a machine and a drive therefor embodying the principles of the present invention;

FIGURE 2 is a side elevational view shown schematically of the mechanism of FIGURE 1;

FIGURE 3 is a fragmentary detailed View of mechanism for shifting the position of the belt on a cone pulley drive;

FIGURES 4 through 6 are graphs illustrating the relationship between creep, torque and belt travel;

FIGURE 7 is a diagrammatic showing of the belt position control mechanism;

FIGURE 8 is a side elevational view shown partially in section of the cone drive pulleys for the mechanism;

FIGURE 9 is a sectional view taken through the axis of one of the cone pulleys and illustrating the input drive for the driven pulley;

FIGURE 10 is a fragmentary elevational view showing a portion of the belt shifting mechanism; and

FIGURE 11 is a fragmentary elevational view with a portion in section and the section taken substantially along line XIXI of FIGURE 10.

On the drawings:

FIGURES 1 and 2 illustrate schematically a wet end of a papermaking machine including a travelling Fourdrinier wire 12 supported on breast and couch rolls 13 and 14 and passing over dewatering apparatus including table rolls 15 and suction fiat boxes 16. The flat boxes have means for applying a vacuum therein shown schematically by a suction line with a valve for variably controlling the suction. Stock is fed onto the travelling wire 12 to form a web W from a headbox 19 which has a variable slice. As above discussed changes in consistency of the stock will vary the driving power required, and other minor changes such as adjustment of the slice or variance of the suction in the suction fiat box will also have an effect in changing of the drive power required. The formed web is picked off the Fourdrinier by a pickup felt 17, and the Fourdrinier is driven by a return roll such as 18.

For driving the Fourdrinier a drive mechanism 20 is employed, driven by a prime mover 21 which drives a line shaft 22. The drive mechanism 20 is operated off the line shaft through bevelled gearing 23 which drives a power input shaft 24.

The power input shaft drives a driving cone pulley 25. The drive includes a driven cone pulley 26 with a drive belt 27 passing over the cone pulleys. The pulleys are arranged with axes parallel and with their tapers extending in opposite directions so that shifting of the belt axially will change the drive speed ratio between the input 4 shaft 24 and an output shaft 28. The position of the drive belt is varied by a belt shifter 29, which is shown in greater detail in FIGURE 3.

In accordance with the invention, a torque measuring device 31 is connected to the output shaft 28 to measure the torque passing through the drive and provides a first signal to a comparing mechanism 30 which provides a second signal for operating the belt shifter. The comparing mechanism 30 is designed in accordance with the known characteristics of creep of the belt 27 and pulleys 25 and 26 as a function of torque. When the torque signal is received, an output signal is generated which will shift the belt 27 an amount to compensate for the change in creep due to change in torque thereby maintaining a constant output speed of the shaft 28.

It will of course be understood that the torque could be measured at other locations in the drive for example at the input shaft 24.

An improved form of belt shifting mechanism 29 is illustrated in FIGURE 3. The belt shifting mechanism includes a carriage 32 having fingers 33 and 34 to be positioned on each side of the belt 27. The carriage slides along parallel smooth cylindrical guide rods 35 and 36 supported on headers 35a and 36a at their ends. The carriage has an internally threaded axially extending bore 32a through which extends a shaft 37 which is threaded at its center portion so that the carriage will be moved axially with rotation of the shaft 37. The shaft rotates within hollow tubes 38 and 39 which are splined at their outer surface and slidably pass through stationary bearings 40 and 41. The headers 35a and 3611 have the splined tubes 38 and 39 fixed thereto. The shaft 37 is driven by a motor 37a which controllably rotates in either direction to vary the position of the belt shifting carriage 32.

The motor 37a is used for rapidly bringing the belt shifting carriage 32 into the proper operating range, and adjustment of the belt to compensate for creep will be performed by a creep compensating cylinder having a piston therein connected to a piston rod 44. The motor 37a is also used for adjustment of the belt independent of the creep compensating cylinder 45 such as must be used in a Fourdrinier machine for quick speed changes such as needed during starting of the machine or during the time a new web is being threaded through the machine.

The creep compensating piston rod 44 is connected to a plate 42 which is secured to the splined tube 39. Thus movement of the piston rod 44 as shown by the arrow will move the spline tubes 38 and 39 with it and also move the motor 37a. The piston rod 44 is shown at the far right of its travel in FIGURE 3 with the plate 42 against the bearing 41, but during operation it will be located somewhere near the midpoint of its range so that movement can occur in either direction for shifting the belt 27 in either direction to compensate for increase or decrease in torque. For convenience of using available pressurized air lines the motor 37a may be a pneumatic motor.

FIGURE 7 illustrates diagrammatically the arrangement for converting the first signal of torque in the output shaft 28 to a displacement signal for positioning the belt. Supply air pressure is provided from a pump 50. A pressure reducer 51 is connected to supply a pressure on the order of 20 p.s.i. to a signal converter 53. The signal converter is fed with an electrical signal from a torque meter and converts the electrical signal to a varying pneumatic signal on the order of 3 to 15 p.s.i. The electric torque meter may be of various constructions known to the art such as that for example shown and described in the copending application of Edgar J. Justus and Leroy H. Busker, Serial No. 184,166, filed April 2, 1962. Another device which may be employed is that known as a dynalog torque recording controller distributed commercially by the Foxboro Company and the features of such a device need not be described in detail. The electrical signal from the torque meter is converted in the comparing device 30 to an electrical signal indicative of the amount of creep of the belt which will occur at the torque being measured and the output signal will provide a shift of the belt position sufficient to compensate for the change in creep. It will of course be recognized that these signals may be converted while in the electrical stage or in the pneumatic stage, and if desired an electrical output signal may be used for positioning the belt with a servo-mechanism.

The output signal for shifting the belt is fed through a line 55 into the creep compensating cylinder 45 to position a piston 59 for operating the piston rod 44. The opposite side of the cylinder is fed with a reference constant pressure on the order of 20 psi supplied from a pressure reducer 54 receiving air from a pressure reducer 52 connected to the supply line. A compression spring 57 may be employed within the cylinder counterbalancing the constant pressure reference air from the pressure reducer 54. Variation in signal pressure delivered to the line 55 will of course position the piston rod 44 to operate the mechanism shown in FIGURE 3.

With the use of a dynalog torque recording controller the proportional output for correcting creep can readily be established. As set forth above, the percent in creep is a linear function of torque transmitted even under dynamic conditions. It is also known that zero torque is zero creep which provides one point on the percent creep torque graph, shown in FIGURE 6, namely the Zero, zero point. By bringing the driven mechanism such as the Fourdrinier to the required speed under no load conditions and then applying full load the change in speed can be observed to determine the percent creep and this provides the second point on the graph x, y, shown in FIG- URE 6. The change in speed of the Fourdrinier due to the applied load must now be compensated for by changing the position of the belt on the cone pulleys. When the required speed has been obtained by shifting the belt it will have been determined the required amount of belt travel (axial distance of belt shift) for creep compensation within the load range and a curve can then be drawn plotting percent creep against belt travel under constant speed conditions (as shown in FIGURE 4) by substituting percent creep as a function of belt travel into the relationship between torque and belt travel (as shown in FIGURE 5). The dynalog torque recording controller of the type above mentioned available from the Foxboro Company is such that upon receiving a pneumatic or electrical signal from a torque meter it will convert this signal into an appropriate output signal to shift the belt on the cone pulleys accordingly. Specific field conditions may be met by adjusting the proportional band of the dynalog in a manner well known to those skilled in the art.

FIGURE 8 shows the drive 20 installed with the input shaft 24 and driving cone pulley 25 mounted in a pit 58 in a floor 59 driving the belt 27. An upright frame 67 supports the driven pulley 26 in the manner illustrated in further detail in FIGURE 9. FIGURE 9 illustrates the driven pulley as driving an output shaft 60 through a bevel gear drive with the pulley driving a pinion shaft 63 carrying a pinion 62 for driving a gear 61 mounted on the output shaft 60. The bevel gear 66 is cantilevered from two main bearings 64 and 65 supporting the pinion shaft 63. The pinion shaft is mounted in a housing 69 which is fastened to the main case or frame 67 in a large bore 68 which is easy to manufacture. A particular feature is a guard 70 over the pulley 26 which is designed with an open side to accommodate the belt run to and from the line shaft pulley 25, whatever the chosen position of the line shaft may be. With this arrangement it is possible to locate the drive so that the centerline of the drive lines up With the centerline of the item to be driven. A clutch may be mounted between the drive and the indrive shaft. Once the drive is installed the belt can be put on and the guard can be rotated to accommodate the belt so that the belt shifter will be in its proper location.

As illustrated in FIGURES 8, 10 and 11 the belt shifter is mounted on the pulley guard 70.

FIGURES l0 and 11 illustrate the belt positioning mechanism 29 in the form slightly modified from the arrangement of FIGURE 3 wherein the belt 27 is posi tioned by fingers such as 74 extending at the sides of the belt. The finger 74 is carried on a carriage 73 provided with dovetail joints to be slidable in a movable slide 71 provided with dovetail joints at its upper end to slide in a support 75 on the guard 70. In the arrangement of FIG- URES 10 and 11 the screw operating range desired for the belt position, to thus move the slide 71 in operating position, and creep compensating movement provided by the cylinder will move the carriage 73. A guard 76 extends downwardly over the slides.

In operation, as illustrated in FIGURE 1, as the load on the Fourdrinier wire 12 changes due to various factors, for example such as change in consistency of the stock, the load on the output shaft 28 will change thus changing the belt creep. This would normally change the speed of the output shaft 28, but with the present arrangement this is immediately compensated for by the belt shifter 29 moving the belt an amount to compensate for the change in creep. The torque measuring device 31 is a constant signal of torque to the comparing device 35 which supplies an output signal to operate the belt shifter 29 and maintain constant speed.

As will be apparent from the foregoing, in accordance with the method of the present invention, the belts on the pulleys are initially located for obtaining a desired output speed with zero creep, and the torque of the output pulley is measured and the belt shifted toward the smaller diameter end of the output pulley an increasing distance as a function of the increase in torque for maintaining uniform output speed. If the output shaft is operating at constant speed and the load is increased thereby increasing the torque, this actuates the automatic control to shift the belt further toward the small end of the output pulley thereby compensating for increased creep at increased torque. This operates to maintain uniform speed of the output shaft.

Thus it will be seen that there has been provided an improved drive mechanism which meets the objectives and advantages above set forth and which maintains a constant speed output from a cone pulley drive without the disadvantages heretofore encountered in other devices such as those employing tachometers for obtaining uniform output speed. It Will of course be recognized that while the mechanism is particularly well adapted to use in combination with the Fourdrinier machine that the drive mechanism may be employed to advantage in other embodiments requiring uniform output speed with change in load.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

We claim as our invention:

1. In a papermaking machine including,

a Fourdrinier wire carried on rolls including a drive roll for driving the wire,

a headbox for distributing stock on the wire,

a suction flat box beneath the wire for dewatering a web formed on the wire,

the power required to drive said wire being changeable during operation, the combination comprising, a driving first cone pulley, a drive belt on said pulleys,

a driven second cone pulley connected to said drive roll,

a prime mover driving the driving pulley at constant speed,

a belt shifter connected for shifting the axial position of the belt relative to the pulleys,

and means for measuring the torque of one of said pulleys and operating the belt shifter changing the position of the belt with change in torque an amount to compensate for change in creep and maintaining a constant speed if travel of the Fourdrinier drive roll.

2. In a papermaking machine including,

a Fourdrinier wire carried on rolls including a drive roll and having changes in drive resistance, the combination comprising,

a driving first cone pulley,

a driven second cone pulley connected to said drive roll,

a drive belt on said pulleys,

a prime mover driving the driving pulley at constant speed,

a belt shifter connected for shifting the axial position of the belt relative to the pulleys,

and means for measuring the torque of one of said pulleys and operating the belt shifter changing the position of the belt with change in torque an amount to compensate for change in creep and maintaining constant speed of the Fourdrinier drive roll.

3. In a drive having input and output cone pulleys with a driving belt means therebetween shiftable axially for changing the speed of the output pulley, the combination comprising,

means for measuring the torque of the drive,

and means shifting the position of the belt means as a function of said torque an amount to compensate for change in creep of the belt means with change in torque.

4. In a drive for a paper machine or the like, the'combination comprising,

first and second cone pulleys positioned so that their taper extends in opposite directions,

a drive belt extending over said pulleys,

driving means connected to said first pulley for operating said first pulley at a uniform speed,

a driven means connected to said second pulley,

a belt shifter connected for shifting the axial position of the belt to change the speed ratio between the pulleys,

and a control connected to said belt shifter measuring the torque of one of said means controlling the belt shifter to compensate for change in belt creep to maintain a constant speed of said driven means.

5. In a drive for a paper machine or the like, the combination comprising,

first and second cone pulleys positioned so that their taper extends in opposite directions,

a drive belt extending over said pulleys,

driving means connected to said first pulley for operating said first pulley at a uniform speed,

a driven means connected to said second pulley,

a belt shifter connected for shifting the axial position of the belt to change the speed ratio between the pulleys,

and means measuring the torque of the driven means and connected to said belt shifter for changing the position of the belt with change in torque to compensate for belt creep and maintain a constant speed of the driven means.

6. In a drive having input and output cone pulleys with a driving belt means therebetween shiftable axially for changing the speed of the output pulley, the combination comprising,

means for measuring the torque of the drive and providing a first output signal which is a function of torque,

a belt shifter for axially changing the position of the belt,

a reference device receiving said first signal and obtaining a creep compensating value in accordance with said first signal for producing a second output signal,

and means controlled by said second signal operating said belt shifter to change the position of the belt an amount to compensate for change in creep and maintaining a constant speed of the output pulley.

7. In a drive having cone pulley with a driving belt therebetween, in combination,

a laterally shiftable belt engaging member for shifting the position of the belt relative to the pulleys,

a first shifting means connected to said member for moving the member a controlled amount,

and a second shifting means connected to said belt engaging member for moving said member a controlled amount,

said second shifting means moving said first shifting means with said belt engaging member.

8. In a device having cone pulleys with a driving belt therebetween, in combination,

a laterally shiftable belt engaging member for shifting the position of the belt relative to the pulleys, first shifting means connected to said member for moving the member a controlled amount including a rotary drive motor and including a rotatable screw element and follower nut element,

said elements connected between said motor and said belt engaging member,

and a second shifting means including a piston and cylinder connected to said belt engaging member for moving said member a controlled distance,

said second shifting means moving said first shifting means with the belt engaging member.

9. In a drive having cone pulleys with a driving belt therebetween, in combination,

a laterally shiftable belt engaging member for shifting the position of the belt relative to the pulleys,

first shifting means connected to said member for moving the member a controlled amount,

second shifting means connected to said belt engaging member for moving said member a controlled amount,

said second shifting means moving said first shifting means With said belt engaging member,

means measuring the torque of the drive, and means connected to said first shifting means and to said measuring means for shifting the belt engaging member as a function of said torque an amount to compensate for change in creep of the belt with change in torque.

10. The method of obtaining a constant speed output in a drive having cone pulleys with a driving member therebetween which comprises compensating for change in belt creep between the driving member and pulleys with change in load by shifting the axial position of the driving member as a function of change in torque to thereby compensate for change in creep and maintain constant output speed.

11. The method of obtaining a constant speed output in a cone pulley drive with an axially shiftable drive belt means between pulleys which comprises measuring the torque of one of the pulleys and changing the position of the belt means as a function of torque an amount to compensate for change in creep with change in said torque.

12. The method of obtaining a constant speed output in a cone pulley drive with an axially shiftable drive belt means between pulleys which comprises positioning the belt mens on the pulleys at a location for obtaining a desired output speed with zero creep, and measuring the torque of one of the pulleys and shifting the belt toward the smaller diameter end of the output pulley an in creasing distance as a function of increase in torque an amount to compensate for increase in belt creep.

13. The method of obtaining a constant speed output in a cone pulley drive with an axially shiftable drive belt means between pulleys which comprises positioning the belt means on the pulleys at a location for obtaining desired output speed with zero creep, and measuring the torque of the output pulley and shifting the belt toward the smaller diameter end of said output pulley an increas ing distance as a function of increase in torque an amount to compensate for increase in belt creep and maintain uniform output speed.

References Cited by the Examiner UNITED STATES PATENTS Weston.

Fryer 74-242.3 Severy et al 74-2423 Warburton 162-256 Merrill 34-121 Yeager 74242.3 Bondurant 74242.3

DON A. WAITE, Primary Examiner. MORRIS O. WOLK, Examiner. 

9. IN A DRIVE HAVING CONE PULLEYS WITH A DRIVING BELT THEREBETWEEN, IN COMBINATION, A LATERALLY SHIFTABLE BELT ENGAGING MEMBER FOR SHIFTING THE POSITION OF THE BELT RELATIVE TO THE PULLEYS, FIRST SHIFTING MEANS CONNECTED TO SAID MEMBER FOR MOVING THE MEMBER A CONTROLLED AMOUNT, SECOND SHIFTING MEANS CONNECTED TO SAID BELT ENGAGING MEMBER FOR MOVING SAID MEMBER A CONTROLLED AMOUNT, SAID SECOND SHIFTING MEANS MOVING SAID FIRST SHIFTING MEANS WITH SAID BELT ENGAGING MEMBER, MEANS MEASURING THE TORQUE OF THE DRIVE, AND MEANS CONNECTED TO SAID FIRST SHIFTING MEANS AND TO SAID MEASURING MEANS FOR SHIFTING THE BELT ENGAGING MEMBER AS A FUNCTION OF SAID TORQUE AN AMOUNT TO COMPENSATE FOR CHANGE IN CREEP OF THE BELT WITH CHANGE IN TORQUE. 